Wet vacuum pump



July 13, 1926.

l. C. JENNINGS WET VACUUM PUMP 6 Sheets- Sheet 1 Filed Jan. 26, 1922 WMATTORNEY5.

INVENTOR 4c Y Wm,

I. C. JENNINGS July 13 1926.

WET VACUUM PUMP Filed Jan. 26.. 1922 6 Sheets-Sheet 5 1c BY Wm, (24

ATTORNEYS.

July 13 1926. 1,592,024

I. C. JENNINGS WET VACUUM PUMP Filed Jan. 2 1922 6 Sheets-Sheet 4INVENTOR BY m, 222;

mefirfw ATTORNEYS.

July 13 1926.

l. c. JENNINGS WET VACUUM PUMP 6 Sheets-Sheet 5 /37 I Filed Jan. 26 1922i ll INVENTOR 6 BY W I ATTORNEYS.

July 13,1926. 1,592,024

v I, c. JENNINGS WET VACUUM PUIIP Filed Jan. 2 1922 (SySheets-Sheet 6 7/I Il"////// INVENTOR M WM,

ATTORNEYS.

'- Patented July is, 1926.

UNITED STATES PATENT OFFICE.

'IRV'ING '0. JENNINGS, SOUTH NORWALK, CONNECTICUT.

WET VACUUM PUMP.

Application filed January 28, 1922. Seria1 No. 532,000.

.The present invention relates tmpuinping apparatus and moreparticularly to apparatus of the type employed for exhausting liquid andgas from a container, for example air and water. Perhaps the largestfield of usefulness resides in abstracting the air and water from thereturns of a, vacuum steam heating system, the air being discharged intothe atmosphere and the water preferably being returned to the boiler.

Heretofore apparatus of this type has comprised a tank into which thereturns from the heating system have been discharged, the pumps and themotor for driving the latter. Because the pumps have beenlocatedindependently of the tank, a more or less com-' mention, the preferredapparatus comprises a tank separated by a partition into twocompartments; and a water and air pump. carried by the tank and havingits inlets directly opening into one of the compartments. The air pumpdischarges into the other compartment and the water pump discharges toany desired point. The motor for driving the pumps is mounted on a baserigid withthe tank and the motor shaft carries the pump impellers. Inthis manner all piping is eliminated and it is possible to employ a pumphaving no bearings except a bearing for packing.

Another feature of the invention consists in the provision of meanswhereby the level of water in one of the compartments of the tank neverfalls below that sufiicient to prime the airy pump.

. Other objects and features of novelty will be apparent from thedescriptions taken in connection with the drawings in which Figure 1 isa -longitudinal section of the pumping unit and part of the tank, therest of the tank being shown in elevation;

Figure '2 is a section on the line 22 of Figure 1, showing the pumpcasings in eleration; v

Figure 3 is a section through the air pump on the line 33 of Figure 1;

Figure 4 is a separate view of the water pump volute housing inelevation from the motor side;

Figure 5 is a plan View of the pump and tank; J

from the pump end, of the passage plate, with the port plate in place;

Figure 7 is a longitudinal section of one end of the motor bearinshowing a modified means of adjusting t e shaft;

Figure 8 is a detail view of the lock washer of Figure 7;

Figure 9 is a View similar to Figure 1 showing a modified form of pumpconstruction;'

Figure 10 is an end elevation of the modified form;

Figure 11 shows the port plate of the modification with theimpeller'dotted in;

Figure 12 is a separate view of the motor end of the volute housingofthe modification;

Figure 13 is a plan of the modified form of pump and tank; and

Figure 14 is a plan or edge view of the air impeller, the port plate andpassage plate being shown. in section taken on the. line -1414 of Figure10.

Referring'to the drawing the embodimentof the invention illustratedtherein comprises essentially a tank A. divided by the partition intotwo compartments 5 and 9. The returns from the heating system areconducted by means of pipe 8 to compartment 5. Associated with the tankA, being aligned with an opening in a side wall'thereof are the twopumps B and C, the former being the water pump for withdrawing the waterfrom the compartment 5 and the latter being the air pump for maintainingthe vacuum in the compartment 5. This latter pump discharges into thecompartment 9 which constitutes a separating chamber for separating thewater from the air and returning the water to the compartment 5. Mountedon a base 14 rigid with the tank A is a motor D the shaft of whichcarries the rotors of the pumps.

Har given a ne de t n Figure 6 is a separate view, in elevationof theapparatus the same will now be described more in detail.

Referring first to Figure 1, A designates the tank which receives airand water from the return main 8 of a vacuum steam heating system. Thistank is divided into two separate compartments 5 and 9 by a web 50 whichencloses one corner, as shown best in Figure 2. The air and water aredrawn into the portion 5 and the portion 9 is used as a separatingchamber to separate the water entrained in the air discharged by the airpump and thereby prevent its loss from the system. This water isautomatically returned to the chamber 5 through a passage 13 governed bya fluid valve 12 which pre vents air from being sucked into the lowpressure chamber 5. Air is discharged to the atmosphere from theseparating chamber 9 through an opening 11. For removin g water from thechamber 5, I use the centrifugal pump A whose rotor or impeller isdenoted by 2, and for removing air a hydroturbine air pump whose rotoris designated by '1. These rotors are keyed to a bronze shaft 49 whichat 30 is rigidly coupledto the shaft 51 of the commercial motor D.

The compartment 5 of the tank isprovided with an opening 52 in the sidewall thereof and the face of the portion of the wall surrounding thesaid opening is milled to form a seat for the volute casing 33 of thecentrifugal pump, shown separately in Figure 4. \Vhen seated, thiscasing closes l the opening 52 except for the port 6 through which thepump draws its supply. The casing 33 is provided with an apron or baflle16 to maintain a definite head of water in the tank which insurespriming of the air pump, as will be later explained. Below the opening52 in the wall of the chamber 5 is a port 17 which registers with aconduit or passage 17 in the casing 33 and supplies priming and make upwater to the air pump. The volute casing 33 is also provided withpassages 7 and 10 registering with corresponding openings in the wall ofthe tank A and providing intake and exhaust passages for the air pump.Seated on the V0- lute casing and bolted thereto is a hollow passageplate 32, shown separately in Figure 6, which is for the purpose ofproviding intake, exhaust and make up water conduits for the air pump.This plate is divided into two passageways between the water and airrotors by a tortuous web 53, one of said passageways 7 surrounding thepump shaft and communicating at one end through the passage 7* with thechamber 5. At its other end the passage 7 communicates with the intakeports 55 of the air pump and thus forms a supply or intake conduit forthe air pump. The passageway 7 is provided also with an opening 17 whichregisters with the passage 17 in the volute casing and thus communicateswith the lower part of the tank through the port 17. \Vater is thusadmitted to the intake conduit of the air pump and as the level cannever be lower than the top of the battle 16, a supply of water isassured for priming the pump. The other passageway 10 in the passageplate communicates with the exhaust ports 54 and leads through thepassage 10 to the separating chamber 9 and thus provides an exhaustconduit for the air pump. The inlet and outlet openin s 7 and 10 areprovided with bafiles 15 an 15 to insure the intake and exhaust of theair at the top of the chambers.

The air pump is provided with a port plate 41, which is seated in arecess provided in the passage plate 32 or, if desired, it may be madeintegral therewith. The rotor chamber is formed in a casing 31 which isseated on the port and passage plates, and bolted to the latter. Thiscasmg is provided with a sleeve 56 and packing gland 57 around theshaft.

The casings 33 and 31 together with passage plate 32 and port plate 41thus constitute a casing for the dual amp, and this casing is mounted onthe tan with openings in direct communication with the interior of thetank through openings in the wall of the tank itself. Just as the twocasings constitute a single casing for a combined liquid and gas pump;so do the rigidly connected liquid and gas rotors form a single rotorfor said dual pump.

It is to be noted that the various stationary parts of the two pumps arebolted or otherwise fastened directly to the tank. All these parts aswell as the tank and motor base are preferably cast. The tank is alsopreferably bolted and doweled to the base 14 of the motor D, whereby thewhole pumping and separating apparatus forms a compact, easilyinstalled, unitary structure. This can be shipped as a unit, and allthat is required in installation is connection to two pipes, the main 8and the boiler feed 39.

An alternative construction of the pump unitis shown in Figs. 9 to 14.This is generally similar to that above described, the chief diilerencebeing that the port plate and passage plate are mounted on the motorside of the pump rather than on the tank side. The volute casing 33 isnot provided with passages through to the air pum and the plate 56 formsthe back plate 0 both pumps. and is mounted in the opening in the volutecasing. The liquid rotor 2, and air rotor 1 are keyed on the shaft asusual, the air rotor chamber being formed in the casing 41 which alsocontains the ports. The passage plate 32 is mounted on the motor side ofthe air pump, and is provided with the web 53 dividing it into twopassages 87 and 38. These form the intake and exhaust passagesrespectively, communicating with the chambers of the'tank A throughpassages 37 and Y38 in a connection 36. Make up water is supplied fromthe tank through pipe 40.

In each construction, the tank extends below the intake of the waterpump to provide a settling pocket thus eliminating a strainer in thereturn mains. closed through an opening 60 or 60.

As is well known, in air pumps of this type, the rotor must move withinits casing and over the port plates without touching these parts and yetwith very small clearance. It has been the custom to provide the pumpwith bronze port plates, casing, and rotor, as well as an expensivebearing to maintain axial adjustment. I eliminate all hearings in thepump, using the motor hearing to support the rotors. I Since mostcommercial motors have considerable end play,

this must be taken up to prevent end play in the pump, and the meansused to take up end play also serve to make with great nicety thenecessary axial adjustment of the pump r clearance.

The motor shaft is provided near each end with a collar 20, see Figs. 1and 7 and the motor has two similar bearings, each comprising a bushing19 adapted to form the bearing surface proper and also to constitute athrust bearin for the collar 20. The usual oil rings are s own at 22. Iuse threadedv collars 24 which may be screwed in or out to position thebushings 19 and consequently theshaft. Each collar is formed with radialnotches 27 into one of which fits the end of a spring clip 61, screwedto the motor end frame, and designed to prevent turning of the collarafter adjustment. If desired, a set screw 21 may be used as anadditional means of retaining the bushing in position. If preferred,alock washer may be used to retain the collar 24, and as shown in Figs.7 and 8 this may be provided with a lug 27 which is bent into a notch27-, and may have two lugs 28,- fitting into recesses 28 in the endframe.

In assembling the apparatus, the volute casing is first placed on thetank, and after the tank has been bolted and doweled to the motor base,the pump shaft, with the rotors in place, and the various plates andeasing loosely assembled, is attached to the motor shaft, and the motorset in place, the motor casing being independent of the pump casing. Thepassage plate carrying the port plate is then bolted to the tank and theair pump casing is pushed back exposing the air rotor to view. Byrotating the shaft and inserting feelers between the rotor and the portplate, it can readily be determined when the shaft is square, the motorbeing shimmed for adjustment and finally bolted and doweled to the base.The shaft is then This pocket may be- .is subjected to great strains.

adjusted axially by turning the'co'llars 24 until the rotor has thedesired clearance, the collars being then locked in position to pre ventturning. The air pump casing can now be bolted in place.

The removable air pump casing greatly facilitates the adjustment of therotors and the thrust bearings not only serve as a means. for makingadjustments but also accurately maintain the adjustments when made andso keep the rotors out of contact with the casing and effectuallyprevent wear.

The unit is designed to operate either continuously or to be controlledby an automatic switch for intermittent operation. Water and air enterthe chamber 5, the water level being prevented from falling below thetop of the bafile 16. This is provided to insure at all times asufiicient head to prime the air pump through the passage 17 and intakeports 55. The water pump draws water through its inlet 6 and dischargesit through the outlet nozzle 33 to the pipe 39, which may lead to theboiler or other desired place. The air pump being primed by the watersupply through pasthrough outlet 11. mall quantities of water areentrained in the air and thus discharged by the air pump, .make up-forwhich is supplied automatically and continuously through the primingconduit. The discharged water is collected in the separating tank, andautomatically returned through valve 12 to chamber 5.

In addition to the structural features enumerated, vacuum pumpingapparatus of this type possesses the advantage that if water comes intothe tank 5 faster-than it can be withdrawn, or if the unit is for anycause shut down, no damage will result. In systems using reciprocatingair pumps excess. water tends to'flood'the air pump, which then expelssolid slugs of water and When the water in the vacuum side of the tank Arises high enough to force water through the passage 17 in largequantities the air pump floods and becomes inoperative to discharge airor water to the atmosphere. In the meantime the pump 2 is withdrawingwater and as soon as the level is sufficiently lowered, the air pumptakes hold and removes air from the system.

goes 'to the atmosphere Because of the fact that the suction pas- Cirthe apron 16 it of course becomes air bound. But when more water comesinto the chamber it supplies the water pump driving out the air throughthe top of the passage 6 and around through passage 7 into the air pump.A small quantity of air will remain in the water pump to be forced outthrough the clearance 7' into the passage 7".

It will be understood that the invention is not limited to theparticular details shown by way of illustration, but that many changesmay be made within the scope of the appended claims. c

Having thus described my invention what is claimed as new and desired tobe secured by Letters Patent is:

1. Pumping apparatus of the character described, including incombination, a tank having two compartments and openings in one wallthereof, there being an opening for each compartment, and a pumpincluding a casing mounted on said tank and having inlet and outletopenings registering with the openings in said wall.

2. Pumping apparatus of the character described, including incombination, a tank having three openings in a wall thereof, a combinedliquid and gas pump secured to said wall and having an inlet for theliquid pump, a gas inlet for the gas pump and a gas outlet for the gaspump, said inlets and outlet severally being in communication with saidopenings.

3. In a pumping apparatus, in combination, a tank, a pump casing mountedon and having openings into the tank, a liquid rotor and a hydro-turbinegas rotor mounted in said casing and adapted to withdraw liquid and gasfrom the tank, and means for priming the gas pump rotor.

4. Pumping apparatus of the character described, including incombination, a tank having four openings in a wall thereof, a liquid andgas pump secured to said wall and having a liquid inlet, a as inlet, agas outlet, and an inlet for supp lying the gas pump with the liquidnecessary for its operation,

the gas pump being of the type requiring liquid for operation, saidinlets and outlet severally being in communication with said openings.

5. Pumping apparatus of the character described, including incombination, a tank having three openings in a wall thereof, a combinedliquid and gas pump including a casing having a liquid inlet, a gasinlet and a gas outlet, and means to secure said casing to said wallwith said inlets and outlet severally in communication with the interiorof said tank through said openings.

6. Pumping apparatus of the character described, including incombination, a tank having a plurality of independent openings in onewall thereof, a combined liquid and gas pump including a casing havingliquid and gas inlets in one side thereof, and means to secure saidcasing to said wall with said inlets severally in communication with theinterior of said tank through said openings.

7. In a umping apparatus, in combination, a tan a pum casing formingpart of the tank, and a hy ro-turbine pump mounted in said casing forwithdrawing fluid from the tank, the tank having means to maintain asupply of liquid for priming the pump.

8. In a pumping apparatus, in combination, a tank having openings, apump casing mounted on the tankhaving an inlet opening in directcommunication with said tank through the first mentioned opening, and aliquid rotor in the casing, the intake of the rotor being below thenormal level of liquid in the tank.

9. Pumping apparatus of the character described, including incombination, a tank having a plurality of independent openings in onewall thereof, a combined liquid and gas pump including a casing, saidgas pump being of the type requiring liquid for its operation, saidcasing having an inlet for the liquid pump, an inlet for the gas pump,and a liquid inlet for supplying the gas pump with the liquid necessaryfor its operation, and means securing said casing to said wall with saidinlets severally in communication with the interior of said tank throughsaid openings.

10. Pumping apparatus of the character described, including incombination, a tank for the reception of liquid and gas havingindependent openings in the wall thereof, a pump casing secured to saidwall and having inlet and outlet openings registering with-.,said firstmentioned openings, and a pump rotor in said casing adapted to removeliquid and gas from said tank.

11. In a pumping apparatus, in combination, a tank comprising areceiving chamber and a separating chamber, a pump casing mounted on thetank and having openings into said chambers, a pump rotor mounted in thecasing adapted to remove gas and liquid from the receiving chamber andto pump gas into the separating chamber.

12. In a pumping apparatus, in combination, a tank comprising areceiving chamber and a separating chamber, a pump casing forming partof the tank, a pum rotor mounted in the casing for with rawing liquidand gas from the tank, means in the tank for maintaining a supply ofliquid for priming the pump, and means in the separating chamber forreturning to the receiving chamber liquid entrained in the gas.

13. In a pumping apparatus, in combination, a tank comprising areceiving chamber and a separating chamber, a pump casing mounted on thetank and having openings into the chambers, a pum rotor in the easingfor removing liquid rom the receiving chamber, a pump rotor in thecasing for pumping gas from the receiving chamber to the separatingchamber, and means in the casing for supplying make-up liquid to the gasrotor.

14. Pumping apparatus of the character described, including incombination, a gas and liquid pump comprising a shaft, a liquid rotorand a gas rotor mounted thereon and a casing including a part having asuction passage for said gas rotor located between said rotors, saidassage being in communication with two in ependent openings through theoutside of the casing, one of said openings being the gas inlet and theother opening for supplying makeup liquid to the gas pump.

15. Pumping apparatus of the character described, lncluding incombination, a tank having a vertical wall with a plurality of openingstherein, a combined rotary liquid and gas pump havin a horizontal shaftand including a casing aving liquid and gas inlets in one side thereof,and means to secure said casing to said wall with said inlets severallyin' communication with the interior of said tank through said openings.

16. In a pumping apparatus, in combination, a unitary structurecomprising a tank, a pump casing and a motor base, a motor mounted onsaid base, a pump rotorln said casing supported by the motor shaft, andmeans in the motor for adjusting the clearance between the pump rotorand casing.

17. In a pumping apparatus, in combination, a unitary structurecomprising a tank, a pump casing and a motor base, a motor mounted onthe base, a pump rotor in the casing supported by the motor shaft, andadjustable thrust bearings in the motor,

18. In a pumping apparatus, in comb1nation, a unitary structurecomprising a tank, a pump casing and a motor base, a motor mountedon thebase, a pump rotor in the casing supported by the motor shaft, and meansin the motor to maintain the axial adjustment of the rotor.

19. In a pumping apparatus, in combination, a unitary structurecomprising a tank, a pump casing and a motor base, a motor on the base,a pump rotor in the casing supported by the motor shaft, part of thecasing being removable to facilitate alignment of the motor.

20. In a pumping apparatus, in comblnation, a unitary structurecomprising a tank, a pump casing and a motor base, a motor on the base,a pump rotor in the casing supported by the motor shaft, part of thecasing being adapted to slide along the shaft to facilitate alignment ofthe motor.

21. Pumping apparatus of the character described, including incombination, a tank having a plurality of openings in one wall thereof,a combined rotary liquid and gas and acasing for said rotors, saidcasing having a suction passage for said gas rotor located between saidrotors and surrounding said shaft, said passage being in communicationwith the tank outside the periphery of said rotors. 23. In a pumpingapparatus, in combinatlon, a tank for the reception of liquid and gas, apump casing forming part of the tank, a liquid ,rotor and a gas rotormounted in said casing, said casing having a suction passage for theliquid rotor and a suction passage for the gas rotor, each of saidpassages being disposed around the shaft and said gas suction passagebeing in communication with said tank outside the periphery of saidrotors.

24. Pumping apparatus of the character described, including incombination, a tank, a pump casing having an inlet in communication withthe interior of said tank and having a stufling box, a motor having itsshaft extending into said casing through said stuffing box, and a rotoron said shaft within said casing, said motor having means for adjustingits shaft axially.

25. Pumping apparatus of the character described, including incombination, a tank having openings in the wall thereof, a pump casingsecured to said tank and having an inlet and outlet openings incommunication with said first mentioned openings and also having astuffing box, a motor having its shaft extending into said casingthrough said stufling box, and a rotor on said shaft within said casing,said motor having means to adjust its shaft axially.

26. Pumping apparatus of the characterv described, including incombination, a tank, a water pump and air pump secured thereto andadapted to withdraw water and air therefrom, the air inlet for said airpump being disposed around the hub of the water rotor and incommunication with said tank laterally of the water pump whereby air inthe water rotor is to some extent withdrawn into said inlet and no airleaks into the water rotor from the air side of the pump and means saidtank.

registering with the first mentioned openings, a second pump casingsecured to the first having openings commumcatmg with some of the secondset of openings thus placing the second pump in communication with saidtank, a motor rigid with the tank having a shaft projecting intosaidcasings, a liquid rotor in one casing, and a gas rotor in the othercasing, said rotors being secured to said shaft.

28. Pumping apparatus of the character described, including incombination, a tank, two rotary pumps secured to said tank and incommunication with the interior thereof, one pump being a liquid pumpand including a casing and rotor, the other pump being a gas pump andincluding a rotor and easing having a passage plate, said plate beindisposed at one side of the gas rotor an provided with gas inlet andoutlet passages therein, andmeans to drive said pumps.

29. Pumping apparatus of the character described, including incombination, a tank having two compartments, a rotary water pump, arotary air pump, said pumps being carried by said tank, the inlet of thewater pump being in communication with one compartment through anopening in the tank, the inlet and discharge of the air pump being incommunication with different compartments, the inlet being incommunication with the same com artment as the water pump inlet and theischarge with the other compartment, and means to drive said pumps.

30. Pumping apparatus of the character described, including incombination, a tank having two compartments with openings in the wallsthereof, a rotary water pump, a rotary air pump, said pumps secured tosaid tank, the inlet of the water pump being in communication with theinterior of one compartment through one of said openings, the casings ofsaid pumps having passages, one connecting the inlet of the air pump andan opening in the same compartment as the water pump inlet, andanother'eonnecting the discharge of the air pump and the othercompartment, and means to drive said pumps.

31. Pumping apparatus of the character described, including incombination, a tank having two compartments, a rotary water pump, arotary air pump, said pumps carried by said tank, the inlet of the waterpump being in communication with onecompartment through an opening inthe tank, the inlet and discharge of the air pump being in communicationwith different compartments, the inlet of the air pump being incommunication with the same compartment as the inlet of the water pump,and the discharge of the air pump with the other compartment, the airpump being of the type employing water for its pumping action, means tosupply said air pump with the water necessary for its operation from'the tank, and means to drive said pumps.

32. Pumping apparatus of the character described, including incombination, a tank having two compartments. with openings in the wallsthereof, a rotary water pump, a rotary air pump, said pumps secured tosaid tank, the inlet of the water pump being in communication with theinterior of one compartment through one of said openings, the casings ofsaid pumps having passages, one connecting the inlet of the air pump andan opening in the same compartment as the water pump inlet, and anotherconnecting the discharge of the air pump and the other compartment, andmeans to drive said pumps, said air pump being of the type employingwater for its pumpim action, and said pump casings having an additionalpassage for supplying the air pump with water necessary for itsoperation from the tank.

33. Pumping apparatus of the character described, including incombination, a tank having two compartments and an opening in the wallthereof, a rotary water pump secured to said tank over said opening, andhaving its inlet directly in communication with said tank through saidopening, an air pump secured to the water pump and including a casing,rotor, and passage plate disposed between the water pump casin and theair pump casing, said air pump fieing of the type employing water forits pumping action, said water pump casing having a passage affordingcommunication between the passage in said plate and one of saidcompartments, this passage constituting a discharge for the air pump,and two other passages in said water pump casing connecting withpassages in said plate and both compartments, one being the inlet andthe other to supply make-up water to the water pump, and means to drivesaid pumps.

34. Pumping apparatus of the character described, including incombination. a tank having two compartments, a liquid pump, and a gaspump, the inlet of the liquid pump being in communication with onecompartment through an opening in the tank, the inlet and discharge ofthe gas pump being in communication with different compartments, theinlet being in communication with the same compartment as the liquidpump inlet and the discharge with the other compartment.

35. Pumping apparatus of the character described, including incombination, a tank having a plurality of independent openings in onewall thereof, a combined liquid and gas pump having a casing providedwith liquid and gas inlets in one side thereof, and means to secure saidcasing to said wall with each inlet in register with one of saidopenlugs.

36. A water and air pumping apparatus a conduit to supply the air pumpwith the water necessary for its operation from the tank arranged at alower level than the inlet to the centrifugal pump, said air pump beingarranged and connected to exhaust the air and maintain a vacuum in thesystem.

37. A water and air pumping apparatus for use in a vacuum steam heatingsystem including in combination, a tank having an opening in a verticalwall thereof, a centrifugal pump secured to said tank to take its supplytherefrom, a rotary air pump of the type requiring water for itsoperation aligned with said centrifugal pump, the rotors of both pumpsbeing mounted on a common horizontally disposed shaft, and a conduit tosupply the air pump with the water necessary for its operation from thetank arranged at a lower level than the inlet to the centrifugal pump,said air pump being arranged and connected to exhaust the air andmaintain a vacuum in the system after the centrifugal pump has drawn allthe water that it can from the tank.

38. A water and air pumping apparatus for use in a vacuum steam heatingsystem including in combination, a tank having an opening in a verticalwall thereof, a centrifugal pump secured to said tank to take its supplytherefrom, a rotary air pump of the type requiring water for itsoperation aligned with said centrlfugal pump, the rotors of both pumpsbeing mounted on a com-' mon horizontally disposed shaft, and a conduitto supply the air pump with the water necessary for its operation fromthe tank' arrangedat a lower level than the inlet to the centrifugalpump, said air pump being arranged and connected to exhaust the air andmaintain a vacuum in the system and so that the water used in the airpump will return to the tank.

39. A water and air pumping apparatus for use in vacuum steam heatingsystems, in-

cluding in combination, a tank having an aperture in a vertical wallthereof, a centrifugal pump casing, a fluid pump casing aligned withsaid centrifugal casing, one of said casings being secured to said tankto takeits supply through said aperture, a common horizontally disposedshaft for said pumps, a water impeller secured to the shaft and Withinthe centrifugal pump casing, a fluid impeller secured to said shaft andwithin the fluid pump casing, the fluid pump being of the type requiringwater for its operation, and having an inlet and outlet disposed forexhausting air from the system, and a conduit for supplying the fluidpump with the water necessary for its operation from water in the tank.

In testimony whereof I hereunto aflix my signature.

IRVING- 0. JENNINGS.

